Page 70 - 2010-2022 hose manufactureing ability and guide
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a. A proof pressure test is normally Expansion occurs if the measurement at
applied to hose for a specified period of the proof pressure is greater than at 10
time. On new hose, the proof pressure is psi (0.069 MPa). Contraction occurs if
usually 50% of the minimum specified the measurement at the proof pressure is
burst except for woven jacket fire hose less than at 10 psi (0.069 MPa).
where the proof pressure is twice the
service test pressure marked on the hose d. Warp is the deviation from a straight
(67% of specified minimum burst). line drawn from fitting to fitting; the
Hydrostatic tests performed on fire hose maximum deviation from this line is
in service should be no higher than the warp. First, a measurement is taken at
service test pressure referred to above. 10 psi (0.069 MPa) and then again at
The regulation of these pressures is the proof pressure. The difference
extremely important so that no between the two, in inches, is the warp.
deteriorating stresses will be applied, Normally this is a feature measured on
thus weakening a normal hose. woven jacket fire hose only.
b. With some type of hose, it is useful to e. Rise is a measure of the height a hose
know how a hose will act under rises from the surface of the test table
pressure. All change in length tests, while under pressure. The difference
except when performed on wire braid or between the rise at 10 psi (0.069 MPa)
wire spiralled hose, are made with and at the proof pressure is reported to
original length measurements taken the nearest 0.25 inch (6.4 mm).
under a pressure of 10 psi (0.069 MPa). Normally, this is a feature measured on
The specified pressure, which is woven jacket fire hose only.
normally the proof pressure, is applied f. Twist is a rotation of the free end of the
and immediate measurement of the hose while under pressure. A first
characteristics desired are taken and reading is taken at 10 psi (0.069 MPa)
recorded. and a second reading at proof pressure.
Percent length change (elongation or The difference, in degrees, between the
contraction) is the difference between 10 psi (0.069 MPa) base and that at the
the length at 10 psi (0.069 MPa) (except proof pressure is the twist. Twist is
wire braided or wire spiralled) and that reported as right twist (to tighten
at the proof pressure times 100 divided couplings) or left twist. Standing at the
by the length at 10 psi (0.069 MPa). pressure inlet and looking toward the
Elongation occurs if the length of the free end of a hose, a clockwise turning
hose under the proof pressure is greater is right twist and counterclockwise is
than at a pressure of 10 psi (0.069 left twist.
MPa). Contraction occurs if the length g. Kink test is a measure of the ability of
at the proof pressure is less than at 10 woven jacket hose to withstand a
psi (0.069 MPa). In testing wire momentary pressure while the hose is
braided or spiralled hose, the proof bent back sharply on itself at a point
pressure is applied and the length approximately 18 inches (457 mm)
recorded. The pressure is then released from one end. Test is made at pressures
and, at the end of 30 seconds, the length ranging from 62% of the proof pressure
is measured; the measurement obtained on sizes 3 inches (76 mm) and 3.5
is termed the “original length.” inches (89 mm) to 87% on sizes under 3
c. Percent change in outside diameter or inches (76 mm). This is a test applied to
circumference is the difference between woven jacket fire hose only.
the outside diameter or circumference at h. Volumetric expansion test is applicable
10 psi (0.069 MPa) and that obtained only to specific types of hose, such as
under the proof pressure times 100 hydraulic or power steering hose, and is
divided by the outside diameter or a measure of its volumetric expansion
circumference at 10 psi (0.069 MPa). under ranges of internal pressure.
RMA/IP-2/2003 49
